<PAGE>

                                                                    Exhibit 10.3

                            FIRST AMENDMENT TO LEASE

                  THIS FIRST AMENDMENT TO LEASE (this "Amendment"), is made as
of November 13, 2001, by and between BDG KINGSBRIDGE L.L.C., a New York limited
liability corporation, having an address c/o Blumenfeld Development Group, Ltd.,
6800 Jericho Turnpike, Suite 102E, Syosset, New York 11791 ("Landlord"), and
ENZON, INC., a Delaware corporation, having an address of 20 Kingsbridge Road,
Piscataway, New Jersey 08854 ("Tenant").

                                    RECITALS

                  WHEREAS, pursuant to that certain Lease Agreement (the "Lease
Agreement") dated June 5, 1992, Holland Realty Corp. ("Holland") leased to
Tenant certain premises (the "Demised Premises") located in Piscataway, New
Jersey, as more particularly described therein;

                  WHEREAS, the Lease Agreement was superseded by that certain
Indenture of Lease dated April 1, 1995 (the "Lease");

                  WHEREAS, Holland and Tenant entered into that certain Option
Agreement dated April 1, 1995 (the "Option Agreement"), pursuant to which Tenant
was granted certain rights to purchase the Demised Premises;

                  WHEREAS, Centennial Properties, L.L.C. ("Centennial")
subsequently purchased the Demised Premises from Holland and succeeded to
Holland's interest as Landlord under the Lease and as optionor under the Option
Agreement;

                  WHEREAS, on or about August 25, 1997, Landlord purchased the
Demised Premises from Centennial and succeeded to Centennial's interest as
Landlord under the Lease and as optionor under the Option Agreement;

                  WHEREAS, Tenant subsequently claimed to have exercised its
option to purchase the Property, which exercise was disputed by Landlord and
ultimately settled between the parties pursuant to that certain Settlement
Agreement effective October 31, 2000.

                  WHEREAS, Landlord and Tenant have agreed to amend the Lease
pursuant to the terms and conditions set forth below.

                  NOW, THEREFORE, in consideration of the sum of ONE DOLLAR
($1.00) paid by Tenant to Landlord and for other good and valuable
consideration, the mutual receipt and legal sufficiency of which is hereby
acknowledged, and intending to be legally bound, the parties agree as follows:

         1. All capitalized terms used herein shall have the meanings ascribed
to them in the Lease unless otherwise specifically set forth herein to the
contrary.

         2. SECTION 2.01 of the Lease is hereby modified to provide that the
term of the Lease and the demise of the Demised Premises shall be extended from
June 15, 2007 to July 31, 2021 (such later date, the "Expiration Date"). The
period commencing as of June 16, 2007 and ending at 11:59 p.m. on July 31, 2021
is herein referred to as the "Restructured Term". The terms "Term" and "Lease
Term" as set forth in the Lease shall hereafter refer to the period beginning on
the Commencement Date (i.e., April 1, 1995) and ending on the Expiration Date
(i.e., July 31, 2021); provided that the "Term" and "Lease Term" shall also
include any renewal term that is properly exercised by Tenant and not rescinded
under Section 35.01.



                                      E-13
<PAGE>

         3. SECTION 3.01 of the Lease is hereby amended and restated in its
entirety as follows:

            "The Tenant shall pay to the Landlord, during the Term without
            counterclaim, deduction or set-off, Basic Rent as set forth herein
            throughout the Term (such rent, the "Term Basic Rent"), payable in
            such coin or currency of the United States of America as at the time
            of payment shall be legal tender for the payment of public and
            private debts."

         4. The table set forth in SECTION 3.02 of the Lease is hereby amended
and restated in its entirety as follows:

--------------------------------------------------------------------------------
PERIOD                                ANNUAL BASIC                MONTHLY BASIC
                                          RENT                        RENT
--------------------------------------------------------------------------------
April 1, 1995-June 15, 1996           $440,002.57                 $36,666.88
--------------------------------------------------------------------------------
June 16, 1996-June 15, 2002           $496,485.57                 $41,373.80
--------------------------------------------------------------------------------
June 16, 2002-June 15, 2007           $581,210.07                 $48,434.17
--------------------------------------------------------------------------------
June 16, 2007-June 15, 2012           $639,331.08                 $53,277.59
--------------------------------------------------------------------------------
June 16, 2012-June 15, 2017           $703,264.18                 $58,605.35
--------------------------------------------------------------------------------
June 16, 2017-July 31, 2021           $773,590.06                 $64,465.84
--------------------------------------------------------------------------------

         5. The following language is added to the end of the first paragraph of
SECTION 7.01 of the Lease:

            "Subject to Section 8.05 hereof, and provided that no Event of
            Default has occurred or is continuing hereunder, in lieu of
            escrowing for Real Estate Taxes, Tenant may, at its option, pay Real
            Estate Taxes on a quarterly basis directly to the municipality not
            less than five (5) days prior to the date on which interest or
            penalties accrue thereon, in which case Tenant shall provide
            Landlord with evidence of such payment no later than the date
            interest or penalties accrue thereon."

         6. The last sentence of SECTION 7.04 is hereby amended and
restated in its entirety as follows:

            "If the refund relates to a tax year that is apportioned between the
            Landlord and the Tenant, such refund shall be apportioned between
            the Landlord and the Tenant after first deducting therefrom the
            reasonable costs and expenses incurred by Tenant in effectuating
            such refund."



                                      E-14
<PAGE>


         7. The last sentence of SECTION 8.01(B) is hereby amended and restated
in its entirety as follows:

            "The aforesaid insurance shall contain customary deductibles, not to
            exceed fifty thousand and NO/100 Dollars ($50,000.00)."

         8. The first sentence of the second paragraph of SECTION 9.02 of the
Lease is hereby deleted and replaced with the following two sentences:

                  "Notwithstanding anything contained herein to the contrary,
            Tenant may, without the need for obtaining Landlord's prior written
            consent (but upon prior notice to Landlord and subject to Tenant's
            compliance with other construction related provisions in this
            lease), make alterations, additions and improvements within the
            Demised Premises which do not affect the building systems (i.e.
            heating, ventilating, plumbing, electrical or other utilities) or
            any structural portion of the Building (including the roof),
            provided that the work is performed in accordance with applicable
            laws and that the cost of any alteration, addition and/or
            improvement (or series of related improvements made within any six
            (6) month period) does not exceed the sum of Forty Thousand and
            NO/100 Dollars ($40,000.00). Nothing in this paragraph shall in any
            way limit the obligations of Tenant under this Lease with respect to
            such permitted alterations, additions or improvements, including,
            without limitation, insurance requirements, prohibitions on liens,
            surrender obligations, and related items."

         9. ARTICLE XI is hereby amended by adding the following paragraph as
new SECTION 11.05:

                  "Notwithstanding anything to the contrary in this Article XI,
            in the event the insurance proceeds made available to Landlord
            following any casualty are insufficient to complete the restoration
            of the Demised Premises, at the election of Tenant exercised within
            ten (10) days after written notice from Landlord of such insurance
            proceeds deficiency, Landlord will nevertheless agree to complete
            such restoration, provided that: (i) simultaneously with such
            election by Tenant, Tenant deposits cash with Landlord in the full
            amount of the insurance proceeds deficiency estimated by Landlord to
            restore the Demised Premises; (ii) the mortgagee of the Demised
            Premises, if any, makes the proceeds of any casualty insurance
            available to the Landlord to restore the Demised Premises and (iii)
            all other conditions to Landlord's obligations to restore under the
            Lease are otherwise satisfied. In the event Landlord restores any
            portion of the Expansion Premises following a casualty, the time
            periods within which Landlord is required to restore the Demised
            Premises under Article XI before Tenant may terminate the Lease
            shall be extended by the additional period of time reasonably
            necessary to restore the Expansion Premises."

         10. The second sentence of SECTION 16.02 of the Lease is hereby deleted
in its entirety.



                                      E-15
<PAGE>



         11. The first four lines of SECTION 16.03 of the lease are hereby
amended and restated in their entirety as follows:

                  "The Landlord shall have a period of fifteen (15) days
            following receipt of the aforementioned notice within which to
            notify the Tenant in writing that Landlord elects either:"

         12. SECTION 16.03(A) of the Lease is hereby amended and restated in its
entirety as follows:

            "If Tenant proposes an assignment of the Lease or a sublease of more
            than fifty percent (50%) of the Demised Premises for substantially
            the balance of the Lease Term, to terminate this Lease as to the
            space so affected as of the date so specified by the Tenant as above
            (with the same effect as if such date was the date fixed herein for
            the expiration of the Term) in which event (1) the Term Basic Rent
            and Tenant's share of all taxes, utilities and other CAM charges
            (currently one hundred percent (100%)) shall be reduced
            proportionately to reflect the reduction in the size of the Demised
            Premises; (2) Landlord shall pay to Tenant the unamortized cost of
            the Tenant Improvements within the deleted portion of the Demised
            Premises (such cost to be amortized over the Lease Term with
            interest at eight percent (8%) per annum) and (3) Tenant will be
            relieved of all further obligations hereunder as to such space
            accruing from and after such date."

        13. SECTION 16.03(B) of the lease is hereby deleted.

        14. The last sentence of SECTION 16.03(C) of the lease is hereby amended
and restated in its entirety as follows:

            "If the rental rate agreed between Tenant and assignee or sublessee
            (computed on the basis of an average square foot rent for the
            Demised Premises and net of normal and reasonable expenses incurred
            by Tenant in the assignment or subleasing effort including
            concessions such as free rent periods and Tenant improvement
            allowances, with such expenses amortized over the term of such
            assignment or sublease at an interest rate of eight percent (8%) per
            annum) is greater than the Term Basic Rent and Additional Rent that
            Tenant must pay Landlord, then all of such excess rental shall be
            shared equally by Landlord and Tenant."

         15. The following language is added to the end of the last paragraph
of SECTION 16.03:

                "As used in this Section 16.03, The phrase "for substantially
                the balance of the Lease Term" shall refer to a term ending
                within the last six (6) months of the Restructured Term."



                                      E-16
<PAGE>



         16. SECTION 17.01 shall be modified to delete both existing notice
addresses for Landlord, and substituting:

                           BDG Kingsbridge L.L.C.
                           c/o Blumenfeld Development Group, Ltd.
                           6800 3ericho Turnpike, Suite 102E
                           Syosset, New York 11791

         17. The following is hereby added as new ARTICLE XXXV of the Lease:

                                  "ARTICLE XXXV

                                    RENEWALS

                  SECTION 35.01. Tenant is hereby granted (i) an option (the
            "First Option") to renew this Lease for an additional five (5) year
            period (the "First Option Period"), which period shall commence on
            the date following the Expiration Date and shall terminate on the
            day preceding the fifth (5th) anniversary of the commencement date
            of such Option Period (such termination date, the "First Option
            Period Termination Date") and (ii) an additional option (the "Second
            Option" and together with the First Option, the "Options") to renew
            this Lease for an additional five (5) year period (the "Second
            Option Period" and together with the First Option Period, the
            "Option Periods"), which period shall commence on the date following
            the First Option Period Termination Date and shall terminate on the
            day preceding the fifth (5th) anniversary of the commencement date
            of such Option Period; both Options and Option Periods shall be
            subject to the following terms and conditions:

                           (A) At the time of the exercise of either Option and
                  at the time of the commencement of either Option Period, no
                  Event of Default shall exist under the terms of this Lease,
                  and Tenant shall be in possession of the Demised Premises
                  pursuant to the terms of this Lease;

                           (B) Notice of Tenant's exercise of (i) the First
                  Option shall be sent to the Landlord, in writing, at least
                  thirteen (13) months prior to the Expiration Date and (ii) the
                  Second Option shall be sent to the Landlord in writing, at
                  least thirteen (13) months prior to the First Option Period
                  Termination Date; TIME HEREBY BEING MADE OF THE ESSENCE WITH
                  RESPECT TO TENANT'S ELECTION OF EITHER OPTION;

                           (C) Each Option Period, to the extent exercised,
                  shall be governed by the same terms and conditions set forth
                  in this Lease with respect to the initial Lease Term, with the
                  exception of Term Basic Rent. Term Basic Rent payable during
                  the Option Periods shall be equal to ninety-five percent (95%)
                  of the fair market rental value of the Demised Premises for a
                  lease renewal term of five (5) years commencing on the
                  commencement date of the applicable Option Period taking into
                  account the other payment obligations of Tenant under this
                  Lease and all other relevant factors (such fair market rental
                  value, as determined in accordance with the provisions of
                  Paragraph (D) below, the "Fair Market Rent");



                                      E-17
<PAGE>

                           (D) Upon Tenant's timely and proper exercise of
                  either Option pursuant to the terms and provisions hereof,
                  Landlord shall, no later than twelve (12) months and ten (10)
                  days prior to the commencement date of the applicable Option
                  Period, notify Tenant in writing of the annual Term Basic Rent
                  to be paid during the applicable Option Period, as determined
                  by Landlord in its sole discretion to be ninety-five percent
                  (95%) of the Fair Market Rent. Tenant shall then have the
                  option, exercisable only within ten (10) days following
                  receipt of Landlord's notice identifying its determination of
                  the Fair Market Rent, TIME HEREBY BEING MADE OF THE ESSENCE
                  WITH RESPECT TO TENANT'S EXERCISE OF SUCH ELECTION, to: (i)
                  affirm its exercise of the applicable Option but dispute
                  Landlord's determination of Fair Market Rent, (ii) affirm its
                  exercise of the applicable Option and accept the Fair Market
                  Rent fixed by Landlord in such notice or (iii) irrevocably
                  rescind its exercise of the applicable Option in which case it
                  shall have no further Options under this Article XXXV.
                  Tenant's failure to respond within such ten (10) day period
                  shall be deemed an election under clause (ii) above. In no
                  event shall Tenant have any right to rescind a previously
                  exercised Option more than ten (10) days after receipt of
                  Landlord's determination of the Term Basic Rent for the
                  applicable Option Periods as aforesaid. In the event Tenant
                  elects to dispute Landlord's determination of Fair Market
                  Rent, the Fair Market Rent shall be determined in accordance
                  with the following procedures and the value as so determined
                  shall be conclusive and binding on the parties:

                  The Fair Market Rent of the Demised Premises shall be
            determined by an appraisal made by a board of three reputable real
            estate appraisers, each of whom shall be actively engaged in the
            appraisal of real property in Middlesex County, and a member of the
            local chapter of the Appraisal Institute, or the successor body
            hereafter constituted and exercising similar functions, and who
            shall have no financial interest in either Landlord or Tenant and
            shall not be an affiliate of either thereof. Of the three
            appraisers, Tenant and Landlord shall each select one appraiser, at
            their sole cost and expense, not later than fifteen (15) days after
            Tenant's election under clause (i) of subparagraph (D) above to
            dispute Landlord's determination of Fair Market Rent and those two
            appraisers shall then select a third appraiser within 15 days after
            the last of the two is appointed. If either Tenant or Landlord fail
            to select an appraiser within the fifteen (15) day period, TIME
            HEREBY BEING MADE OF THE ESSENCE WITH RESPECT TO EITHER PARTY'S
            SELECTION OF AN APPRAISER, the appraiser timely selected by the
            other party, if any, shall determine the Fair Market Rent without
            regard to the three (3) appraiser averaging method that would
            otherwise apply. Each appraiser shall render its written appraisal
            within thirty (30) days after the selection of the third appraiser.
            In the event Landlord or Tenant's appraiser fails to render a
            decision within such thirty (30) day period, Fair Market Rent shall
            be deemed to be the average of the other two appraisals timely
            delivered. If the determination of any two or all three of the
            appraisers shall be identical in amount, such amount shall be deemed
            to be the Fair Market Rent of the Demised Premises. If the
            determination of all three appraisers shall be different in amount,
            the highest appraised value shall be averaged with the middle value
            (such average being hereinafter referred to as "Sum A"), the lowest
            appraised value shall be averaged with the middle value (such
            average being hereinafter referred to as "Sum B"), and the Fair
            Market Rent of the Demised Premises shall be determined as follows:



                                      E-18
<PAGE>


                         (i) If neither Sum A nor Sum B differs from the middle
            appraised value by more than 10% of such middle appraised value,
            then the Fair Market Rent of the Demised Premises shall be deemed to
            be the average of the three appraisals.

                         (ii) If either Sum A or Sum B (but not both of such
            sums) differs from the middle appraised value by more than 10% of
            such middle appraised value, then the Fair Market Rent of the
            Demised Premises shall be deemed to be the average of the middle
            appraised value and the appraised value closest in amount to such
            middle value; and

                         (iii) If both Sum A and Sum B differ from the middle
            appraised value by more than 10% of such middle appraised value,
            then the Fair Market Rent of the Demised Premises shall be deemed to
            be the middle appraised value.

                     The parties shall each pay for the cost of their own
            appointed appraiser and shall share equally in the cost of the third
            appraiser. While the parties intend to have the Fair Market Rent
            determined prior to the commencement of the applicable Option
            Period, in the event, that notwithstanding the provisions set forth
            above, either Option Period shall commence prior to resolution of
            the proper Fair Market Rent with respect to such Option Period,
            Tenant shall pay the Term Basic Rent in effect immediately prior to
            the applicable Option Period (without regard to any abatement of
            rent then in effect pursuant to the terms of the Lease) as Term
            Basic Rent during such Option Period, subject to prospective and
            retroactive adjustments upon the final determination of Fair Market
            Rent as aforesaid.

            Notwithstanding any of the foregoing to the contrary, (a) Tenant
            shall not be permitted to exercise the Second Option Period in the
            event Tenant shall have failed to exercise the First Option Period
            pursuant to the terms and conditions set forth above, (b) Tenant
            hereby agrees that the Options and Option Periods are personal to
            Tenant and may not be assigned to any other party, and (c) except as
            otherwise provided herein, Tenant shall not be entitled to revoke
            either Option after exercising the same."



                                      E-19
<PAGE>



         18. The following is hereby added as new ARTICLE XXXVI of the Lease:

                                 "ARTICLE XXXVI

                                    EXPANSION

                      SECTION 36.01. Tenant shall have the one-time option (such
             option, the "Expansion Option") to expand the Demised Premises
             (such expansion, the "Expansion") pursuant to and in accordance
             with the terms and conditions set forth below:

                                (A) At the time of the exercise of the Expansion
                      Option, no Event of Default shall then exist under the
                      terms of this Lease and Tenant shall be in possession of
                      the Demised Premises pursuant to the terms of this Lease;

                                (B) Subject to the provisions of Section 36.03,
                      the Expansion shall be performed and completed at Tenant's
                      sole cost and expense and Tenant shall pay any and all
                      reasonable costs actually incurred by Landlord and paid to
                      unaffiliated third parties for review and oversight of the
                      construction work and documentation with respect to the
                      Expansion including reasonable legal fees and costs. In
                      addition, Tenant shall be solely responsible for obtaining
                      all permits, licenses and governmental approvals for the
                      Expansion, including, without limitation, any and all
                      zoning permits, variances and building permits (such
                      permits, licenses and approvals, the "Consents"). Landlord
                      will cooperate with Tenant's efforts to obtain Consents at
                      no material cost to Landlord. Landlord makes no
                      representations or warranties with respect to Tenant's
                      ability to obtain any required Consents or Tenant's
                      ability to construct all or any portion of the Expansion.
                      Tenant's inability to obtain any Consents or to construct
                      the Expansion shall in no way effect this Lease;

                                (C) Tenant shall exercise the Expansion Option,
                      if at all, on or prior to JULY 31, 2016 by delivering to
                      Landlord written notice of Tenant's intent to expand the
                      Demised Premises, which notice shall be accompanied by (1)
                      preliminary plans and specifications with respect to
                      Expansion (which plans and specifications shall include
                      the materials to be used in connection with the
                      Expansion), (ii) in the event Tenant shall exercise the
                      Expansion Option on or prior to JULY 31, 2006, Tenant's
                      election with respect to the Landlord's Contribution (as
                      defined in Section 36.03 below), (iii) in the event Tenant
                      shall request to have Landlord make the Landlord's
                      Contribution, audited financial statements of Tenant for
                      Tenant's most recently completed fiscal year and certified
                      financial statements for any completed fiscal quarters
                      from and after the most recently completed fiscal year,
                      and (iv) such other information as Landlord may request in
                      its reasonable discretion;




                                      E-20
<PAGE>

                                (D) Tenant's preliminary plans and
                      specifications with respect to the Expansion shall be
                      subject to the prior written consent of Landlord, which
                      consent shall not be unreasonably withheld, conditioned or
                      delayed. Landlord must respond to submissions (i) as to
                      the initial submission, within forty-five (45) days after
                      Tenant's initial submission of a complete set of
                      preliminary plans and specifications; and (ii) thereafter
                      for all submissions within thirty (30) days after any
                      submissions pertaining to any structural work or
                      mechanical or electrical systems and within fifteen (15)
                      days after any other submissions. Notwithstanding any of
                      the foregoing to the contrary, Landlord may (i) withhold
                      such consent in the event Landlord determines, in its
                      reasonable discretion, that the Expansion, as depicted in
                      such plans and specifications, will (a) impair the
                      marketability or value of the Demised Premises, (b) impair
                      the structural integrity or base building systems of the
                      Demised Premises, or (c) violate any applicable law or
                      (ii) delay such consent until Tenant reasonably provides
                      Landlord with any information that Landlord may require
                      with respect to the Expansion pursuant to Paragraph (C)
                      above;

                                (E) In the event Tenant shall request that
                      Landlord make the Landlord's Contribution under Paragraph
                      (C) above, Landlord shall review and either approve or
                      reject the financial statements required under Paragraph
                      (C) above within thirty (30) days after receipt of the
                      same. Landlord may reject such financial statements (in
                      which case it shall not be required to pay the Landlord's
                      Contribution,) only if it determines that Tenant's market
                      capitalization, tangible net worth and earnings as
                      depicted in such financial statements are not at least
                      equivalent to Tenant's market capitalization, tangible net
                      worth and earnings as of the date of this Amendment; in
                      the event Landlord rejects the financial statements and
                      thus does not agree to pay the Landlord's Contribution,
                      Tenant may rescind its exercise of the Expansion Option
                      within thirty (30) days after written notification from
                      Landlord of its rejection of Tenant's financial statements
                      and refusal to fund the Landlord's Contribution;

                                (F) In the event Landlord approves the
                      preliminary plans and specifications submitted in
                      accordance with Paragraph (D) above, Tenant shall, prior
                      to the commencement of the construction of the Expansion,
                      submit to Landlord (i) final, stamped construction
                      drawings and specifications with respect to the Expansion
                      (and from and after the commencement of such construction,
                      Tenant shall submit to Landlord any and all amendments,
                      modifications and/or revisions to such drawings and
                      specifications) for Landlord's approval, which shall not
                      be unreasonably withheld, conditioned or delayed (provided
                      that the same shall be substantially similar to the
                      previously approved preliminary plans and specifications)
                      and (ii) any building permits required for the Expansion.
                      In addition, upon the commencement of Tenant's
                      construction of the Expansion, Tenant shall work
                      diligently to complete the Expansion (a) in accordance
                      with the approved drawings, plans and specifications, (b)



                                      E-21
<PAGE>


                      in accordance with any and all applicable laws, and (c) in
                      a lien free, good and workmanlike manner within two
                      hundred and seventy days (270) after receipt of the
                      building permit, subject to extension as a result of any
                      Force Majeure. Tenant shall reasonably document to
                      Landlord within ten (10) days after the occurrence of any
                      Force Majeure event, the nature of the event, its
                      anticipated impact on the construction schedule and
                      Tenant's plan to mitigate such delay. All work with
                      respect to the Expansion shall be performed by licensed
                      and insured contractors. Landlord hereby reserves the
                      right, to be exercised in its reasonable discretion, to
                      approve the general contractor and any subcontractors
                      performing structural or mechanical work in connection
                      with the Expansion;

                                (G) Landlord shall have the right to inspect the
                      progress of any and all work with respect to the
                      Expansion;

                                (H) The Expansion shall be deemed completed on
                      the date (the "Expansion Completion Date") on which Tenant
                      shall deliver to Landlord (i) a final certificate of
                      occupancy for the Demised Premises comprising the
                      Expansion (the "Expansion Premises") from the applicable
                      governmental authority and (ii) a certificate from
                      Tenant's licensed architect indicating that the Expansion
                      Premises have been built in accordance with the
                      construction drawings and specifications for the Expansion
                      Premises previously submitted to and approved by Landlord.
                      Without limiting any other provisions set forth herein,
                      from and after the Expansion Completion Date the term the
                      "Demised Premises" shall be deemed to include the
                      Expansion Premises, provided that, notwithstanding any of
                      the provisions of the Lease to the contrary (a) Landlord
                      shall not be obligated to maintain any insurance with
                      respect to the Expansion Premises except to the same
                      extent Landlord insures the Demised Premises now (but with
                      an increase in value to reflect the addition of the
                      Expansion Premises) and Tenant shall be obligated to
                      insure the Expansion Premises to the same extent Tenant is
                      obligated to insure the Demised Premises now, (b) Landlord
                      shall not be obligated to maintain, or repair the
                      Expansion Premises but in the event of a casualty it shall
                      restore the Expansion Premises to the same extent Landlord
                      restores the Demised Premises now, and (c) Tenant shall
                      not be permitted to (1) abate or offset rent with respect
                      to the Expansion Premises except to the extent that any
                      loss of rent is actually covered by rental income
                      insurance maintained by Landlord for the Demised Premises
                      (or to the extent the rental loss would have been covered
                      had Landlord carried the rental loss insurance required
                      under Section 8.02 of the Lease) or (2) terminate this
                      Lease due to any casualty or condemnation affecting only
                      the Expansion Premises regardless of whether such right
                      shall exist with respect to the balance of the Demised
                      Premises; however, in the event Tenant validly terminates
                      the Lease for the balance of the Demised Premises pursuant
                      to the terms of the Lease, Tenant shall also be required
                      to terminate the Lease with regards to the Expansion
                      Premises;



                                      E-22
<PAGE>


                                (I) During any period of construction hereunder,
                      Tenant shall maintain Builder's All-Risk Insurance in form
                      and substance acceptable to Landlord in its reasonable
                      discretion, which insurance shall be in an amount equal to
                      the full replacement cost of the Expansion Premises; and

                                (J) Within thirty (30) days of the Expansion
                      Completion Date, (i) Tenant shall provide Landlord with
                      (a) final lien waivers and affidavits from all
                      materialmen, mechanics, suppliers, subcontractors,
                      contractors or other parties providing labor or materials
                      in connection with the Expansion, evidencing that such
                      party has been paid in full with respect to any work it
                      may have performed with respect to the Expansion and (b) a
                      release of any existing mechanic's (or similar) liens
                      against the Expansion Premises with respect to work done
                      or materials provided in connection with the Expansion,
                      which release shall be evidenced by the removal of any
                      exceptions to Landlord's title policy relating to such
                      liens and (ii) the parties shall execute an amendment to
                      this Lease setting forth (a) the total square footage of
                      the Demised Premises (to be determined in accordance with
                      BOMA standards) and (b) the revised Basic Rent (to be
                      determined in accordance with (1) Section 36.02 or Section
                      36.03 hereof, as applicable).

                      SECTION 36.02. In the event Tenant exercises the Expansion
             Option, the annual Term Basic Rent due hereunder shall increase on
             the earlier to occur of (i) the date which is two hundred and
             seventy(270) days after Tenant shall receive a building permit with
             respect to the Expansion Premises or (ii) the Expansion Completion
             Date (such earlier date, the "Section 36.02 Rent Commencement
             Date"), by an amount equal to the product of $5.50 times the total
             rentable square footage area of the Expansion Premises, which total
             rentable square footage area shall be determined by Landlord based
             on (a) the actual size of the completed Expansion Premises, if and
             when completed or (b) until the Expansion Premises are completed,
             the size of the completed Expansion Premises as estimated in the
             latest drawings and specifications approved by Landlord with
             respect to the Expansion Premises. The annual Term Basic Rent for
             the Expansion Premises (as adjusted pursuant to Section 36.03
             below) shall increase by five percent (5%) as of (1) the first day
             of the calendar month marking the fifth (5th) anniversary of the
             Section 36.02 Rent Commencement Date (such date, the "Section 36.02
             Adjustment Date") and (2) each succeeding fifth (5th) anniversary
             of the Section 36.02 Adjustment Date during the Term. In the event
             such rental obligation shall commence prior to the Expansion
             Completion Date, Term Basic Rent shall be appropriately adjusted
             (both prospectively and retroactively) on the Expansion Completion
             Date. The Expansion Premises shall be measured in accordance with
             BOMA standards.



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                      SECTION 36.03. In the event Tenant exercises the Expansion
             Option on or prior to JULY 31, 2006, Landlord shall contribute, at
             Tenant's option and in accordance with the provisions of Section
             36.01 (and subject to the conditions therein), an amount equal to
             $35.00 per rentable square foot of the completed Expansion Premises
             not to exceed Three Hundred Fifty Thousand and NO/100 Dollars
             ($350,000.00) (such amount, the "Landlord's Contribution"). Tenant
             shall make such election, if at all, at the same time Tenant
             exercises the Expansion Option pursuant to the provisions of
             Section 36.01(C) hereof. Upon such election, the annual Term Basic
             Rent otherwise payable under Section 36.02 above for the first ten
             thousand (10,000) rentable square feet of the Expansion Premises
             shall increase on the earlier to occur of (i) the first day of the
             first month following Landlord's payment of the Landlord
             Contribution or (ii) regardless of whether the Expansion Completion
             Date shall have occurred, July 31, 2006 (the earlier of such dates,
             the "Section 36.03 Rent Commencement Date") by an amount equal to
             the product of $4.20 times the total square footage area of the
             Expansion Premises not to exceed 10,000 square feet (as determined
             pursuant to the provisions of Section 36.03), which amount shall be
             in addition to any increase payable under Section 36.02 above (but
             only with respect to the first 10,000 square feet of the Expansion
             Premises) and shall become due and payable in accordance herewith
             regardless of whether the Term Basic Rent for such space has
             commenced under Section 36.02. Landlord shall pay the Landlord's
             Contribution within thirty (30) days after the Expansion Completion
             Date, provided that, (a) no Event of Default shall then exist under
             the terms and provisions of this Lease, including, without
             limitation, any of the obligations set forth in this Article XXXVI,
             (b) Tenant shall then be in possession of the Demised Premises,
             including the Expansion Premises, pursuant to the terms of this
             Lease, (c) there shall not have been any material adverse change in
             Tenant's financial condition from the date on which Landlord shall
             have approved such condition pursuant to Section 36.01(E) above (as
             determined based on Landlord's review of Tenant's audited financial
             statements for Tenant's most recently completed fiscal year (prior
             to the Expansion Completion Date) and certified financial
             statements for any completed fiscal quarters from and after the
             most recently completed fiscal year), (d) Tenant shall have
             delivered to Landlord a complete set of "as-built" construction
             drawings with respect to the Expansion Premises, and (e) Tenant
             shall have complied with each of the conditions precedent to the
             Expansion Completion Date (as set forth in Section 36.01(H)
             above).

                      SECTION 36.04. Without limiting any of the provisions set
             forth herein, including, without limitation, the provisions of
             Section 8.04 hereof, Tenant shall indemnify and save Landlord
             harmless against and from all liabilities, claims, suits, fines,
             penalties, damages, losses, fees, costs and expenses (including,
             reasonable attorney's fees) which may be imposed upon, incurred by
             or asserted against Landlord by reason of (i) any act or failure to
             act by Tenant with respect to or in connection with the Expansion
             or the Expansion Premises, or (ii) the failure of Tenant to comply
             with any of the provisions of this Article XXXVI.



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<PAGE>


                      SECTION 36.05. Tenant hereby agrees that the expansion
             rights discussed herein are personal to Tenant and may not be
             assigned to any other party. Tenant further agrees that upon the
             termination or earlier expiration of this Lease, Tenant shall (i)
             assign to Landlord any third party manufacturer's warranties and
             (ii) deliver copies of all operating manuals, with respect to any
             systems located on the Expansion Premises.

                      SECTION 36.06. Any material default under this Article
             XXXVI which shall continue beyond the applicable notice and cure
             periods in Article XV of the Lease shall be deemed an Event of
             Default and shall entitle Landlord to exercise any and all rights
             and remedies it may have under this Lease."

                      SECTION 36.07. Promptly following Tenant's exercise of its
             Expansion Option, Landlord shall provide Tenant with copies of any
             plans or specifications for the Demised Premises which Landlord has
             in its possession. Landlord shall have no responsibility for the
             accuracy or completeness of such drawings or specifications and
             expressly disclaims any warranty with respect thereto. Landlord
             makes no representation as to its title to such plans or
             specifications."

         19. In connection with the negotiation and execution of this Amendment,
Landlord and Tenant each represents to the other that it has not dealt with any
real estate broker other than Julien J. Studley, Inc. ("JJSI"). Landlord hereby
agrees that it shall pay a commission to JJSI in accordance with a separate
written commission agreement with JJSI. Landlord and Tenant each hereby
indemnifies the other and holds the other harmless from and against any claim
for a commission or other fee made by any broker with whom the indemnifying
party has dealt, other than JJSI.

         20. Except as modified and amended by this Amendment, all of the terms,
covenants and conditions of the Lease are hereby ratified and confirmed and
shall continue to be and remain in full and effect.

         21. This Amendment shall be governed by and construed in accordance
with the laws of the State of New Jersey.

         22. This Amendment may not be modified, amended or terminated nor may
any of its provisions be waived except by an agreement in writing signed by the
party against whom enforcement of any modification, amendment, termination or
waiver is sought.

         23. The covenants, agreements, terms, provisions and conditions
contained in this Amendment shall be binding upon and inure to the benefit of
the parties hereto and their respective permitted successors and assigns.

         24. This Amendment maybe executed in counterparts which, when taken
together, shall constitute one and the same original.

         25. Notwithstanding anything to the contrary in Section 9.02 of the
Lease, Tenant shall not be required to remove any alterations, additions or
improvements to the Demised Premises first constructed after the date of this
Amendment (except Tenant's furniture and trade fixtures) at the expiration or
termination of this Lease unless Landlord advises Tenant of such requirement at
the time of Landlord's consent to the same if Landlord's consent is required
hereunder (or, if Landlord's consent is not required, within thirty (30) days
after Tenant's written notice of its intention to perform the same which notice
shall identify the nature of the work). In no event shall Tenant be required to
remove any structural portions of the Expansion, which hereafter may be
constructed under Article 36.



                                      E-25
<PAGE>



         26. Landlord and Tenant shall execute a memorandum of this Lease and
any amendments hereto. Tenant may record such memorandum at its sole cost and
expense.

         27. As a condition of this Amendment Landlord shall obtain a
subordination, non-disturbance and attornment agreement from its current lender
with respect to the Lease as amended hereby consistent with Section 14.01 of the
Lease. In the event Landlord has not obtained such agreement within forty-five
(45) days after the full execution hereof, Tenant may, within ten (10) days
thereafter, terminate this Amendment by written notice to Landlord (time being
of the essence), otherwise this Amendment shall remain in full force and effect
and Tenant shall be deemed to have waived the condition in this Section 27. In
addition, the parties acknowledge that this Amendment is subject to the consent
of Landlord's current lender. In the event Landlord has not obtained the written
consent of such lender within 15 days after the date hereof (whether by joinder
hereto or separate agreement), Landlord shall promptly notify Tenant of such
failure and thereupon this Amendment shall automatically become null and void
but the existing Lease shall remain in full force and effect.

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                  IN WITNESS WHEREOF, the parties hereto have caused this
Amendment to be executed as of the day and year first above written.

                                  LANDLORD:

                                  BDG KINGSBRIDGE L.L.C.
                                  By: BDG Kingsbridge, Inc. its General Manager



                                  By:   /s/ Jonathan E. Cohen
                                      ------------------------------------------
                                      Name: Jonathan E. Cohen
                                      Its:  Vice President




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<PAGE>

                                  TENANT:

                                  ENZON, INC.


                                  By:   /s/ Arthur Higgins
                                      ------------------------------------------
                                      Name: Arthur Higgins
                                      Its:  President/CEO




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